Backrest folding assembly and seat

Abstract

The utility model provides a backrest folding assembly and a seat. The backrest folding assembly comprises a fixing piece, an upper connecting rod, a lower connecting rod, a turning plate fixing piece, a middle connecting rod and a protective plate; one ends of the upper connecting rod and the lower connecting rod are rotationally connected with the fixing piece, and the other ends of the upper connecting rod and the lower connecting rod are rotationally connected with the turning plate fixing piece; and the protective plate is rotationally connected with the upper connecting rod and the middle connecting rod. The backrest folding assembly is unfolded and folded through rotary connection among the fixing piece, the upper connecting rod, the lower connecting rod and the turning plate fixing piece, the number of parts is small, and the manufacturing cost is low. Meanwhile, by arranging the middle connecting rod and the protection plate, the protection effect is achieved in the folding process of the backrest folding assembly, and safety is improved.

Description

Technical Field

[0001] The present application relates to the field of seating, and in particular to a backrest folding assembly and seating. Background Art

[0002] As people's living standards continue to improve, many different types of seats have appeared on the market. Seats can include furniture that provides rest, such as sofas, beds, chairs or office chairs. Traditional seats use a simple fixed connection between the backrest and the flap, which cannot be folded or adjusted in angle, limiting the usage scenarios and taking up a large amount of space. Existing seats use hydraulic systems or electric systems to fold the backrest folding assembly, but these designs make the structure of the backrest folding assembly complex, with a large number of parts and high manufacturing costs. At the same time, there is no protective plate on the backrest folding assembly of the seat, which can easily cause users to be pinched during the folding process of the backrest and the flap, resulting in low safety.

[0003] Therefore, it is necessary to provide an improved backrest folding assembly and seat to solve the above problems. Utility Model Content

[0004] The present application provides a backrest folding assembly and a seat with low cost and high safety.

[0005] The present application provides a backrest folding assembly, including a fixing part, an upper connecting rod, a lower connecting rod, a flap fixing part, an intermediate connecting rod and a protective plate; one end of the upper connecting rod and the lower connecting rod are both rotatably connected to the fixing part, and the other end of the upper connecting rod and the lower connecting rod are both rotatably connected to the flap fixing part; the intermediate connecting rod is rotatably connected to the lower connecting rod, and the protective plate is rotatably connected to the upper connecting rod and the intermediate connecting rod.

[0006] Furthermore, the protective plate and the flap fixing member are respectively located on the inner and outer sides of the upper connecting rod and the lower connecting rod, and the flipping directions of the protective plate and the flap fixing member are the same.

[0007] Furthermore, when unfolded, the bottom of the flap fixing member and the protective plate are lifted up and moved closer to the fixing member, and the top of the flap fixing member and the protective plate are lifted up and moved away from the fixing member.

[0008] Furthermore, the protective plate is constructed so as to block a gap formed by the upper connecting rod, the lower connecting rod and the flap fixing member when the backrest folding assembly is unfolded or folded.

[0009] Furthermore, the protective plate includes a top edge, a first side edge, a bottom edge and a second side edge connected in sequence, the top edge and the bottom edge are arranged opposite to each other, and the first side edge and the second side edge are arranged opposite to each other; the length of the bottom edge is greater than the length of the top edge.

[0010] Furthermore, when the backrest folding assembly is unfolded, the first side edge is flush with the upper edge of the upper connecting rod, the second side edge is located below the upper connecting rod, the bottom edge is located in front of the fixing member, and the protective plate covers the upper part of the lower connecting rod; when the backrest folding assembly is folded, the first side edge is located in front of the fixing member, and the first side edge and the second side edge are respectively located on both sides of the upper connecting rod; the protective plate covers the flap fixing member.

[0011] Furthermore, the protective plate includes a first fixing portion, a second fixing portion and a first bending portion connecting the first fixing portion and the second fixing portion; the first fixing portion is rotatably connected to the upper connecting rod, and the connection point between the protective plate and the upper connecting rod is located on the first fixing portion; the second fixing portion is rotatably connected to the intermediate connecting rod, and the connection point between the protective plate and the intermediate connecting rod is located on the second fixing portion.

[0012] Furthermore, the flap fixing member includes a fixing portion and a connecting portion fixed together, the connecting portion is perpendicular to the fixing portion, and the connecting portion is rotatably connected to the upper connecting rod and the lower connecting rod respectively.

[0013] Furthermore, the intermediate connecting rod includes a first connecting part, a second connecting part and a second bending part connecting the first connecting part and the second connecting part; the first connecting part is rotatably connected to the lower connecting rod, and the connection point between the intermediate connecting rod and the lower connecting rod is located on the first connecting part; the second connecting part is rotatably connected to the second fixed part, and the connection point between the protective plate and the intermediate connecting rod is located on the second connecting part.

[0014] Furthermore, the lower connecting rod includes a first mounting portion, a second mounting portion and a main body portion connecting the first mounting portion and the second mounting portion; the first mounting portion is rotatably connected to the intermediate connecting rod and the flap fixing member respectively; the main body portion is arc-shaped, and the main body portion protrudes in a direction away from the upper connecting rod; the second mounting portion is rotatably connected to the bottom of the fixing member.

[0015] The present application also provides a seat, comprising a backrest assembly, a flap assembly and the above-mentioned backrest folding assembly, wherein the fixing member is fixedly connected to the backrest assembly, and the flap fixing member is fixedly connected to the flap assembly.

[0016] Furthermore, when the backrest folding assembly is folded, the upper connecting rod, the lower connecting rod, the flap fixing member and the protective plate are folded between the side panel of the backrest assembly and the flap assembly, and are all arranged along the inclination direction of the side panel.

[0017] Furthermore, when the backrest folding assembly is unfolded, the edge of the protective plate fits against the front edge of the backrest assembly, and the protective plate and the backrest assembly together block the gap formed by the fixing member and the upper connecting rod.

[0018] The present invention realizes the expansion and folding of the backrest folding assembly by rotating the connection between the fixing member, the upper connecting rod, the lower connecting rod, the intermediate connecting rod, the flap fixing member, and the protective plate, which has a small number of parts and low manufacturing cost. At the same time, the provision of the intermediate connecting rod and the protective plate provides protection during the folding process of the backrest folding assembly, thereby improving the safety of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a front view of the backrest folding assembly of the present application in the unfolded state.

[0020] Figure 2 yes Figure 1 A schematic diagram of the backrest folding assembly from another perspective is shown.

[0021] Figure 3 yes Figure 1 A side view of the fold-down backrest assembly is shown.

[0022] Figure 4 yes Figure 1 The diagram shows a fold-down backrest assembly without a protective plate.

[0023] Figure 5 yes Figure 1 The diagram shown is a schematic diagram of the backrest folding assembly during the folding process.

[0024] Figure 6 It is a front view of the backrest folding assembly of the present application in the folded state.

[0025] Figure 7 yes Figure 6 A schematic diagram of the backrest folding assembly from another perspective is shown.

[0026] Figure 8 yes Figure 6 A side view of the fold-down backrest assembly is shown.

[0027] Figure 9 yes Figure 1 Schematic diagram of the lower link of the backrest folding assembly shown.

[0028] Figure 10 yes Figure 1 A schematic diagram of the flap fixing member of the backrest folding assembly is shown.

[0029] Figure 11 yes Figure 1 Schematic diagram of the middle link of the backrest folding assembly shown.

[0030] Figure 12 yes Figure 1 Schematic diagram of the protective plate of the fold-down backrest assembly is shown.

[0031] Figure 13 This is a schematic diagram of the seat of the present application in the folded state.

[0032] Figure 14 This is a schematic diagram of the seat of the present application in a state where the flap is unfolded.

[0033] Description of Figure Numbers:

[0034] 100, backrest assembly; 101, side panel; 102, back panel; 103, storage space; 104, front edge; 200, flap assembly; 201, groove; 202, storage hole; 300, seat; 10, fixing member; 11, mounting hole; 12, first fixing hole; 13, second fixing hole; 20, upper connecting rod; 21, connecting hole; 22, connecting hole; 23, connecting hole; 30, lower connecting rod; 31, first mounting portion; 311, first mounting hole; 312, second mounting hole; 32, main body; 33, second mounting portion; 331, third mounting hole; 40, flap fixing member; 41, fixing portion; 411, third fixing hole; 412, third Four fixing holes; 42, connecting part; 421, fourth mounting hole; 422, fifth mounting hole; 50, intermediate connecting rod; 51, first connecting part; 511, first through-hole; 52, second connecting part; 521, second through-hole; 53, second bending part; 60, protective plate; 601, first fixing part; 602, second fixing part; 603, first bending part; 604, third through-hole; 605, fourth through-hole; 61, top edge; 62, first side edge; 63, bottom edge; 64, second side edge; 70, connecting point; 71, connecting point; 72, connecting point; 73, connecting point; 74, connecting point; 75, connecting point; 76, connecting point; 77, connecting point. DETAILED DESCRIPTION

[0035] Here, the technical solutions in the embodiments (or "implementations") of the present application will be clearly and completely described in conjunction with the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0036] If there are terms related to directional indications or positional relationships in the embodiments of this application (such as up, down, left, right, front, back, inside, outside, top, bottom, center, vertical, horizontal, longitudinal, transverse, length, width, counterclockwise, clockwise, axial, radial, circumferential, etc.), such terms are only used to explain the relative positional relationship, movement, etc. between the components in a specific posture (as shown in the accompanying drawings); if the specific posture changes, the directional indication or positional relationship will also change accordingly. In addition, the terms "first" and "second" in the embodiments of this application are only used for the purpose of convenience of description and should not be understood as indicating or implying relative importance.

[0037] See also Figures 1 to 5 As shown, the backrest folding assembly includes a fixing member 10, an upper connecting rod 20, a lower connecting rod 30, a flap fixing member 40, an intermediate connecting rod 50, and a protective plate 60. One end of the upper connecting rod 20 and the lower connecting rod 30 are both rotatably connected to the fixing member 10, and the other end of the upper connecting rod 20 and the lower connecting rod 30 are both rotatably connected to the flap fixing member 40. The intermediate connecting rod 50 is rotatably connected to the lower connecting rod 30, and the protective plate 60 is rotatably connected to the upper connecting rod 20 and the intermediate connecting rod 50. A connection point 70 is formed between the fixing member 10, the upper connecting rod 20, the lower connecting rod 30, the flap fixing member 40, the intermediate connecting rod 50, and the protective plate 60.

[0038] The fixing member 10 is in the shape of a long straight rod and is provided with a mounting hole 11. The number of mounting holes 11 can be one or more. When there is only one mounting hole 11, it should be an elongated hole to limit the position of the fixing member 10. When there are multiple mounting holes 11, they can be round holes or a combination of round holes and elongated holes. A first fixing hole 12 and a second fixing hole 13 are provided at the top and bottom of the fixing member 10, respectively.

[0039] The upper connecting rod 20 is a long, straight rod with three connecting holes 21, 22, and 23. Connecting holes 21 and 23 are located at either end of the upper connecting rod 20, with connecting hole 22 located between them. The distance between connecting holes 22 and 23 is smaller than the distance between connecting holes 21 and 22. The upper connecting rod 20 is riveted to the top of the fixing member 10. The first fixing hole 12 is aligned with the connecting hole 21, and a rivet is inserted into the first fixing hole 12 and the connecting hole 21 to connect the fixing member 10 and the upper connecting rod 20.

[0040] The fixing member 10 and the upper connecting rod 20 are formed into a long straight rod or a rod-like shape. This allows the gap and angle between the fixing member 10 and the upper connecting rod 20 to be smaller when the folding backrest assembly is folded, thereby reducing the space occupied. Furthermore, the fixing member 10 and the upper connecting rod 20 can also be configured as curved or arcuate connecting rods to meet aesthetic or design requirements.

[0041] See also Figure 9 As shown, the lower link 30 includes a first mounting portion 31, a second mounting portion 33, and a main portion 32 connecting the first and second mounting portions 31, 33. The main portion 32 is arcuate and protrudes away from the upper link 20. The first mounting portion 31 defines a first mounting hole 311 and a second mounting hole 312. The second mounting portion 33 defines a third mounting hole 331. The second fixing hole 13 is aligned with the third mounting hole 331. Rivets are assembled into the second fixing hole 13 and the third mounting hole 331 to rivet the fixing member 10 to the second mounting portion 33.

[0042] See also Figure 10 As shown, the flap fixing member 40 includes a fixing portion 41 and a connecting portion 42 fixed together, with the connecting portion 42 being perpendicular to the fixing portion 41. The fixing portion 41 is provided with a third fixing hole 411 and a fourth fixing hole 412. The connecting portion 42 is provided with a fourth mounting hole 421 and a fifth mounting hole 422. The fourth mounting hole 421 is aligned with the second mounting hole 312. Rivets are assembled into the fourth mounting hole 421 and the second mounting hole 312 to rivet the connecting portion 42 to the first mounting portion 31. The fifth mounting hole 422 is aligned with the connecting hole 23. Rivets are assembled into the fifth mounting hole 422 and the connecting hole 23 to rivet the connecting portion 42 to the upper connecting rod 20.

[0043] See also Figure 11 As shown, the intermediate connecting rod 50 includes a first connecting portion 51, a second connecting portion 52, and a second bent portion 53 connecting the first connecting portion 51 and the second connecting portion 52. A first through-hole 511 is defined in the first connecting portion 51, and a second through-hole 521 is defined in the second connecting portion 52. The first through-hole 511 is aligned with the first mounting hole 311. Rivets are assembled into the first through-hole 511 and the first mounting hole 311 to rivet the first connecting portion 51 to the first mounting portion 31. The second connecting portion 52 is secured to the protective plate 60.

[0044] See also Figure 12 As shown, the protective plate 60 includes a top edge 61, a first side edge 62, a bottom edge 63, and a second side edge 64, which are connected in sequence. The top edge 61 and the bottom edge 63 are disposed opposite each other, and the first side edge 62 and the second side edge 64 are disposed opposite each other. The length of the bottom edge 63 is greater than that of the top edge 61. The length of the first side edge 62 and the second side edge 64 are similar, and both are smooth curves.

[0045] The protective plate 60 includes a first fixing portion 601, a second fixing portion 602, and a first bent portion 603 connecting the first fixing portion 601 and the second fixing portion 602. The first fixing portion 601 is provided with a third through-hole 604, which is aligned with the connecting hole 22. A rivet is assembled through the third through-hole 604 and the connecting hole 22 to rivet the first fixing portion 601 to the upper connecting rod 20. The second fixing portion 602 is provided with a fourth through-hole 605, which is aligned with the second through-hole 521. A rivet is assembled through the fourth through-hole 605 and the second through-hole 521 to rivet the second fixing portion 602 to the second connecting portion 52.

[0046] The first bent portion 603 of the protective plate 60 allows the first fixing portion 601 and the second fixing portion 602 to be parallel and spaced apart when viewed from the side of the folding backrest assembly. This prevents friction or collision between the protective plate 60 and the rivets on the lower link 30 when the folding backrest assembly is folded, reducing noise and extending service life.

[0047] The connection points 70 include connection points 71, 72, 73, 74, 75, 76, and 77. The upper link 20 is riveted to the first fixing portion 601 to form the connection point 71. The upper link 20 is riveted to the connecting portion 42 to form the connection point 72. The second fixing portion 602 is riveted to the second connecting portion 52 to form the connection point 73. The first connecting portion 51 is riveted to the first mounting portion 31 to form the connection point 74. The first mounting portion 31 is riveted to the connecting portion 42 to form the connection point 75. The top of the fixing member 10 is riveted to the upper link 20 to form the connection point 76. The bottom of the fixing member 10 is riveted to the second mounting portion 33 to form the connection point 77.

[0048] Connection point 71 is close to connection point 72. Connection point 73 is located in the middle of protective plate 60. The distance between connection point 74 and connection point 73 is close to the distance between connection point 74 and connection point 75. Connection point 72 and connection point 75 are located at both ends of connecting portion 42 respectively.

[0049] Please also see Figures 6 to 8 As shown, when the backrest folding assembly is unfolded, the bottom of the flap fixing member 40 and the protective plate 60 are raised and approach the fixing member 10, while the top of the flap fixing member 40 and the protective plate 60 are raised and away from the fixing member 10. The first side edge 62 is flush with the upper edge of the upper link 20, and the second side edge 64 is located below the upper link 20. The bottom edge 63 is located in front of the fixing member 10. The protective plate 60 covers the upper portion of the lower link 30. The first side edge 62 being flush with the upper edge of the upper link 20 means that the overall trend of the first side edge 62 is to approach the upper edge of the upper link 20. In some embodiments, the first side edge 62 may be slightly higher or slightly lower than the upper edge of the upper link 20.

[0050] When the backrest folding assembly is folded, the bottoms of the flap fixing member 40 and the protective plate 60 are lowered and away from the fixing member 10, while the tops of the flap fixing member 40 and the protective plate 60 are lowered and closer to the fixing member 10. The first side 62 is located in front of the fixing member 10, and the first side 62 and the second side 64 are respectively located on either side of the upper connecting rod 20. The protective plate 60 covers the flap fixing member 40.

[0051] The flap fixture 40 and protective plate 60 remain positioned in front of the fixture 10 during the folding process. The protective plate 60 and flap fixture 40 are located on the inner and outer sides of the upper link 20 and lower link 30, respectively, and rotate in the same direction as the flap fixture 40. When the backrest folding assembly is deployed or retracted, the protective plate 60 blocks the gap formed by the upper link 20, lower link 30, and flap fixture 40.

[0052] See also Figure 13 and Figure 14 As shown, the present application also provides a seat comprising a backrest assembly 100, a flap assembly 200, a seat portion 300, and the aforementioned folding backrest assembly. The flap assembly 200 is foldable relative to the backrest assembly 100. The backrest assembly 100 is fixed to the seat portion 300, with the flap assembly 200 positioned above the seat portion 300. The fixing member 10 is fixedly connected to the backrest assembly 100, and the flap fixing member 40 is fixedly connected to the flap assembly 200.

[0053] The backrest assembly 100 includes two side panels 101 and a back panel 102. The two side panels 101 are arranged opposite to each other and are both fixed to the back panel 102. The two side panels 101 and the back panel 102 enclose a storage space 103. When the backrest folding assembly is folded, the flap assembly 200 and part of the backrest folding assembly are accommodated in the storage space 103, and the flap assembly 200 is parallel to the front edge 104 of the side panel 101. The upper connecting rod 20, the lower connecting rod 30, the flap fixing member 40 and the protective plate 60 are all arranged along the inclination direction of the side panel 101, that is, along the length direction of the front edge 104. The inclination angle of the upper connecting rod 20, the lower connecting rod 30, the flap fixing member 40 and the protective plate 60 in the folded state is close to the inclination angle of the side panel 101.

[0054] When the folding backrest assembly is deployed, the flap assembly 200 and a portion of the folding backrest assembly protrude outside the accommodating space 103. The protective plate 60 is located in front of the side panel 101, with its bottom edge 63 abutting the front edge 104. Together, the protective plate 60 and the side panel 101 block the gap between the fixing member 10 and the upper connecting rod 20. The protective plate 60 generally blocks the gap formed by the side panel 101, the upper connecting rod 20, and the lower connecting rod 30.

[0055] A groove 201 is defined on the side of the flap assembly 200, into which the fixing portion 41 is inserted. The thickness of the fixing portion 41 is less than or equal to the width of the groove 201. The width of the connecting portion 42 is less than or equal to the thickness of the flap assembly 200. The flap assembly 200 is provided with two storage holes 202. When the flap assembly 200 is unfolded, the storage holes 202 are provided for the placement of items such as water cups and tea cups. The number of storage holes 202 can also be one or more. The storage holes 202 can also be configured as through holes or semi-enclosed holes.

[0056] The present invention achieves the deployment and folding of the backrest folding assembly by rotating the connection between the fixing member 10, the upper connecting rod 20, the lower connecting rod 30, the intermediate connecting rod 50, the flap fixing member 40, and the protective plate 60. This reduces the number of parts and reduces manufacturing costs. Furthermore, the intermediate connecting rod 50 and the protective plate 60 provide protection during the folding process of the backrest folding assembly, preventing accidental pinching injuries to the user and improving safety.

[0057] It should be noted that the technical solutions or technical features described in the above embodiments can be combined or supplemented with each other without conflict. The scope of protection of this application is not limited to the precise structures described in the above embodiments and shown in the accompanying drawings; all modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this application shall be included in the scope of protection of this application.

Claims

1. A backrest folding assembly, characterized in that: It includes a fixing part, an upper connecting rod, a lower connecting rod, a flap fixing part, an intermediate connecting rod and a protective plate; one end of the upper connecting rod and the lower connecting rod are both rotatably connected to the fixing part, and the other end of the upper connecting rod and the lower connecting rod are both rotatably connected to the flap fixing part; the intermediate connecting rod is rotatably connected to the lower connecting rod, and the protective plate is rotatably connected to the upper connecting rod and the intermediate connecting rod.

2. The backrest folding assembly according to claim 1, characterized in that: The protective plate and the flap fixing member are respectively located on the inner and outer sides of the upper connecting rod and the lower connecting rod, and the flipping directions of the protective plate and the flap fixing member are the same.

3. The backrest folding assembly according to claim 1, characterized in that: When unfolded, the bottom of the flap fixing member and the protective plate are lifted up and moved closer to the fixing member, and the top of the flap fixing member and the protective plate are lifted up and moved away from the fixing member.

4. The backrest folding assembly according to claim 1, characterized in that: The protective plate is constructed so as to block the gap formed by the upper connecting rod, the lower connecting rod and the flap fixing member when the backrest folding assembly is unfolded or folded.

5. The backrest folding assembly according to claim 4, characterized in that: The protective plate includes a top edge, a first side edge, a bottom edge and a second side edge connected in sequence, the top edge is arranged opposite to the bottom edge, and the first side edge is arranged opposite to the second side edge; the length of the bottom edge is greater than the length of the top edge.

6. The backrest folding assembly according to claim 5, characterized in that: When the backrest folding assembly is unfolded, the first side edge is flush with the upper edge of the upper connecting rod, the second side edge is located below the upper connecting rod, the bottom edge is located in front of the fixing member, and the protective plate covers the upper part of the lower connecting rod; when the backrest folding assembly is folded, the first side edge is located in front of the fixing member, the first side edge and the second side edge are respectively located on both sides of the upper connecting rod; the protective plate covers the flap fixing member.

7. The backrest folding assembly according to claim 1, characterized in that: The protective plate includes a first fixing portion, a second fixing portion and a first bending portion connecting the first fixing portion and the second fixing portion; the first fixing portion is rotatably connected to the upper connecting rod, and the connection point between the protective plate and the upper connecting rod is located on the first fixing portion; the second fixing portion is rotatably connected to the intermediate connecting rod, and the connection point between the protective plate and the intermediate connecting rod is located on the second fixing portion.

8. The backrest folding assembly according to claim 1, characterized in that: The flap fixing member includes a fixing portion and a connecting portion fixed together, the connecting portion is perpendicular to the fixing portion, and the connecting portion is rotatably connected to the upper connecting rod and the lower connecting rod respectively.

9. The backrest folding assembly according to claim 7, characterized in that: The intermediate connecting rod includes a first connecting part, a second connecting part and a second bending part connecting the first connecting part and the second connecting part; the first connecting part is rotatably connected to the lower connecting rod, and the connection point between the intermediate connecting rod and the lower connecting rod is located on the first connecting part; the second connecting part is rotatably connected to the second fixed part, and the connection point between the protective plate and the intermediate connecting rod is located on the second connecting part.

10. The backrest folding assembly according to claim 1, characterized in that: The lower connecting rod includes a first mounting portion, a second mounting portion and a main body portion connecting the first mounting portion and the second mounting portion; the first mounting portion is rotatably connected to the intermediate connecting rod and the flap fixing member respectively; the main body portion is arc-shaped, and the main body portion protrudes in a direction away from the upper connecting rod; the second mounting portion is rotatably connected to the bottom of the fixing member.

11. A seat, characterized in that: It comprises a backrest assembly, a flap assembly and a backrest folding assembly as claimed in any one of claims 1 to 10, the fixing member is fixedly connected to the backrest assembly, and the flap fixing member is fixedly connected to the flap assembly.

12. The sitting device according to claim 11, characterized in that: When the backrest folding assembly is folded, the upper connecting rod, the lower connecting rod, the flap fixing member and the protective plate are folded between the side plate of the backrest assembly and the flap assembly, and are all arranged along the inclination direction of the side plate.

13. The sitting tool according to claim 12, characterized in that: When the backrest folding assembly is unfolded, the edge of the protective plate is in contact with the front edge of the backrest assembly, and the protective plate and the backrest assembly jointly block the gap formed by the fixing member and the upper connecting rod.

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